Vaporization and multifragmentation in the reaction 1.2 GeV p + Cu and Ag

Reactions of 1.2 GeV antiprotons with Cu and Ag targets have been studied. It was found that in such reactions, excitation energies are generated in excess of the total binding energy of the nuclei involved. Accordingly, one observes in these reactions the onset of vaporization and multifragmentation processes. In the p + Cu reaction, the vaporization is observed to set in at about 7.5 MeV/nucleon. However, its probability remains relatively small and below 15% up to the highest excitation energies identified in the present studies (approximately 15 MeV/nucleon). The threshold excitation energy for multifragmentation processes, defined as the detection of at least 3 intermediate mass fragments, is observed at about 4 MeV/nucleon for both studied reactions. Multifragmentation is seen to account for no more than approximately 5% and 20% of the corresponding inclusive yield for Cu and Ag targets, respectively.